I can't fully move one of my KPLs over until LED addressing is enabled (no, this post isn't about that!) but while I was messing with it I noticed there are a couple other issues

One of the buttons on my KPL is a 'volume' button (i've got a play/pause, volume, previous track, next track, setup in the middle 4). With X10 each of those buttons was assigned an F3-6 code, and I had fake devices in my list that matched those codes. With X10 I had a trigger type 'Device State Changed' to 'Different Brightness Level'. Moving to Insteon, since there is no 'device' linked to the button, I made a type 'Insteon Command Received', and 'Brighten', then I had to duplicate the event and set it to 'Dim'. It would be nice if there was a "Brighten or Dim" combo for the received filter.

Which then moves to the next issue that I could use a suggestion on. My AppleScript would check the brightness of the 'device' at the X10 address I had assigned to the KPL button, and then set the volume in iTunes to match. In the new Insteon world, how would I replicate that? There is no 'device' with the button, so there is nothing I can track the brightness of.
Is the only option to start using more variables in place of 'dummy devices'?

Good questions and interesting point. There is no way to setup a phantom or virtual INSTEON device which can track a brightness for you. The way INSTEON sends dim/brighten commands is different than X10, so without a real receiving INSTEON device Indigo cannot know what the dim/brigthen delta amount is. Point being, Indigo does not know that you have held the button down for 1 second versus or 5 seconds and thus cannot translate that into a brightness delta. It works when there is a receiving INSTEON device because Indigo queries the receiving device for its new brightness state after you let go of the button.

The way I do it is to setup Trigger Actions for On, Double Tap On, Off, and Double Tap Off (and not Brighten or Dim). For the On/Off (single tap) commands I change the volume a little (2%) and for the Double Tap I change the volume more (7%). At the KeypadLinc itself I don't press and hold the buttons -- I do a single tap for small adjustments and I tap quickly for larger adjustments.

The sample database file included with 2.0 has examples of this (controlling iTunes from a KPL). You can manually make a copy of the sample file and open it up to take a look:

/Library/Application Support/Perceptive Automation/Indigo 2/Indigo Server/Contents/Resources/Sample House.indiDb

You'll need to cntrl-click on the IndigoServer file and choose Show Package Contents to drill down into the Resources folder.

Regards,
Matt